Dearomatization of 3-Aminophenols for Synthesis of Spiro[chromane-3,1'-cyclohexane]-2',4'-dien-6'-ones via Hydride Transfer Strategy-Enabled [5+1] Annulations.

The Sc(OTf)3-catalyzed dearomative [5+1] annulations between readily available 3-aminophenols and O-alkyl ortho-oxybenzaldehydes were developed for synthesis of spiro[chromane-3,1'-cyclohexane]-2',4'-dien-6'-ones. The "two-birds-with-one-stone" strategy was disclosed by the dearomatization of phenols and direct α-C(sp3)-H bond functionalization of oxygen through cascade condensation/[1,5]-hydride transfer/dearomative-cyclization process. In addition, the antifungal activity assay and derivatizations of products were conducted to further enrich the utility of the structure.

Photocatalytic Ketyl Radical Initiated Cketyl -Csp2 /Csp3 Coupling on ZnIn2 S4.

Visible-light-driven C-C bond formation utilizing ketyl radical (Cketyl ) species has attracted increasing attention recently, as it provides a direct route for the synthesis of complex molecules. However, the most-developed homogeneous photocatalytic systems for the generation and utilization of ketyl radicals usually entail noble metal-based (e. g., Ru and Ir) photosensitizers, which suffer from not only high cost but also potential degradation and hence pose challenges in product separation and purification. In contrast, readily accessible, inexpensive, and recyclable semiconductors represent a class of attractive and alternative photocatalysts but remain much less explored for photocatalytic ketyl radical initiated C-C bond formation. This work demonstrates that a wide range of industrially important chemicals, including substituted chromanes and tertiary alcohols, can be produced on ZnIn2 S4 under visible light irradiation through intramolecular cyclization (Cketyl -Csp2 ) and intermolecular cross-coupling (Cketyl -Csp3 ) reactions, respectively, using ketyl radicals. A suite of experimental studies aided by computational investigation were carried out to shed light on the mechanistic insights of these two types of ketyl radical initiated C-C coupling reactions on ZnIn2 S4 .

Three new chromanes and one new flavone C-glycoside from Mallotus apelta.

Three new chromanes, malloapeltas J-L (1-3), and one new flavone C-glycoside, malloflavoside (4), together with four known compounds, apigenin 6-C-ß-D-xylopyranosyl-8-C-α-L-arabinopyranoside (5), apigenin 6-C-ß-D-glucopyranosyl-8-C-α-L-arabinopyranoside (6), apigenin 7-O-ß-D-apiofuranosyl-(1→2)-ß-D-glucopyranoside (7), and acantrifoside E (8) were isolated from the methanol extract of the leaves of Mallotus apelta. Their chemical structures were determined using spectroscopic methods, including 1D, 2D NMR, and HR-ESI-MS methods. All the isolated compounds were evaluated their cytotoxic activity against human prostate cancer (PC-3) and human breast cancer (MCF-7) cells, but none of them showed cytotoxicities on both human cancer cell lines.

Structure-activity and structure-property relationship studies of spirocyclic chromanes with antimalarial activity.

Malaria is a prevalent and lethal disease. The fast emergence and spread of resistance to current therapies is a major concern and the development of a novel line of therapy that could overcome, the problem of drug resistance, is imperative. Screening of a set of compounds with drug/natural product-based sub-structural motifs led to the identification of spirocyclic chroman-4-one 1 with promising antimalarial activity against the chloroquine-resistant Dd2 and chloroquine-sensitive 3D7 strains of the parasite. Extensive structure-activity and structure-property relationship studies were conducted to identify the essential features necessary for its activity and properties.

New chromanone derivatives containing thiazoles: Synthesis and antitumor activity evaluation on A549 lung cancer cell line.

Novel 2-[2-(chroman-4-ylidene)hydrazinyl]-4/5-substituted thiazole derivatives (2a-i) were synthesized and investigated for their anticancer activity. Cytotoxic activity on A549 and NIH/3T3 cell lines was determined, most of the compounds exhibited high cytotoxic profile with selectivity. Selected compounds 2b, 2c, 2e, 2g, 2h, and 2i were tested to determine induction of apoptosis, mitochondrial membrane depolarization, and cell cycle arrest. The results showed that the compounds induced apoptosis intrinsically that they triggered loss of mitochondrial potential through increasing the accumulation of cells in G2/M. Besides, intrinsic apoptotic pathway was supported by down-regulation of anti-apoptotic protein Bcl-2 and up-regulation of proapoptotic protein Bax. Molecular docking study for compounds 2b, 2c, and 2g was promoted experimental outcomes.

Apparent 6-endo-trig Carbofluorination of Alkenes Enabled by Palladium-Based Dyotropic Rearrangement.

Alkene difunctionalization featuring an intramolecular carbometallation step has been developed into a powerful transformation in organic synthesis. The 5-exo-trig carbometallation is in general highly favored over the alternative 6-endo-trig cyclization. We report herein a formal 6-endo-trig carbofluorination protocol by combining the conventional 5-exo-trig carbopalladation with a chemoselective 1,2-aryl/Pd dyotropic rearrangement. Treatment of 2-(2-alkylallyloxy)phenyl boronic acid derivatives in the presence of a catalytic amount of Pd(dba)2 , 4,4'-di-tert-butyl-2,2'-bipyridine and Selectfluor affords chromanes with concurrent generation of a tertiary alkyl fluoride function. A σ-alkyl-PdII species resulting from the 5-exo-trig carbopalladation process is isolated and characterized by X-ray crystallographic analysis. Its oxidation to PdIV complex triggers the chemoselective dyotropic rearrangement leading to the ring expansion product.

Synthesis and Evaluation of Trypanocidal Activity of Chromane-Type Compounds and Acetophenones.

American trypanosomiasis (Chagas disease) caused by the Trypanosoma cruzi parasite, is a severe health problem in different regions of Latin America and is currently reported to be spreading to Europe, North America, Japan, and Australia, due to the migration of populations from South and Central America. At present, there is no vaccine available and chemotherapeutic options are reduced to nifurtimox and benznidazole. Therefore, the discovery of new molecules is urgently needed to initiate the drug development process. Some acetophenones and chalcones, as well as chromane-type substances, such as chromones and flavones, are natural products that have been studied as trypanocides, but the relationships between structure and activity are not yet fully understood. In this work, 26 compounds were synthesized to determine the effect of hydroxyl and isoprenyl substituents on trypanocide activity. One of the compounds showed interesting activity against a resistant strain of T. cruzi, with a half effective concentration of 18.3 µM ± 1.1 and an index of selectivity > 10.9.

Chromane Derivatives from Underground Parts of Iris tenuifolia and Their In Vitro Antimicrobial, Cytotoxicity and Antiproliferative Evaluation.

Phytochemical investigation of the ethanol extract of underground parts of Iris tenuifolia Pall. afforded five new compounds; an unusual macrolide termed moniristenulide (1), 5-methoxy-6,7-methylenedioxy-4-O-2'-cycloflavan (2), 5,7,2',3'-tetrahydroxyflavanone (3), 5-hydroxy-6,7-dimethoxyisoflavone-2'-O-ß-d-glucopyranoside (9), 5,2',3'-dihydroxy-6,7-dimethoxyisoflavone (10), along with seven known compounds (4-8, 11-12). The structures of all purified compounds were established by analysis of 1D and 2D NMR spectroscopy and HR-ESI-MS. The antimicrobial activity of the compounds 1-3, 5, 9, and 10 was investigated using the agar diffusion method against fungi, Gram-positive and Gram-negative bacteria. In consequence, new compound 3 was found to possess the highest antibacterial activity against Enterococcus faecalis VRE and Mycobacterium vaccae. Cell proliferation and cytotoxicity tests were also applied on all isolated compounds and plant crude extract in vitro with the result of potent inhibitory effect against leukemia cells. In particular, the newly discovered isoflavone 10 was active against both of the leukemia cells K-562 and THP-1 while 4-6 of the flavanone type compounds were active against only THP-1.

Quantitative Structure-Activity Relationships of Natural-Product-Inspired, Aminoalkyl-Substituted 1-Benzopyrans as Novel Antiplasmodial Agents.

On the basis of the finding that various aminoalkyl-substituted chromene and chromane derivatives possess strong and highly selective in vitro bioactivity against Plasmodium falciparum, the pathogen responsible for tropical malaria, we performed a structure-activity relationship study for such compounds. With structures and activity data of 52 congeneric compounds from our recent studies, we performed a three-dimensional quantitative structure-activity relationship (3D-QSAR) study using the comparative molecular field analysis (CoMFA) approach as implemented in the Open3DQSAR software. The resulting model displayed excellent internal and good external predictive power as well as good robustness. Besides insights into the molecular interactions and structural features influencing the antiplasmodial activity, this model now provides the possibility to predict the activity of further untested compounds to guide our further synthetic efforts to develop even more potent antiplasmodial chromenes/chromanes.

A brief overview on recent advances in spiro[chromane-2,4'-piperidine]-4(3H)-one-functionalized compounds in medicinal chemistry research.

The spiro[chromane-2,4'-piperidine]-4(3H)-one is an important pharmacophore. It is a structural component in many drugs, drug candidates (or lead compounds) and various biochemical reagents. This review demonstrated an impressive progress in syntheses of spiro[chromane-2,4'-piperidine]-4(3H)-one-derived compoundsin the recent years and focuses on features of their biological relevance's. The prospects for the development of new biologically active substances containing a spiro[chromane-2,4'-piperidine]-4(3H)-one pharmacophore are analyzed and briefly discussed in terms of its structure, reaction, mechanism, scope and potential utility.

Chromane Enantiomers from the Flower Buds of Tussilago farfara L. and Assignments of Their Absolute Configurations.

Fourteen chromane derivatives of seven pairs of enantiomers (1-14) have been obtained from the ethanolic extract of the flower buds of Tussilago farfara L. Their structures with absolute configurations have been elucidated by detailed spectroscopic analyses, chemical methods, and particularly comparison of experimental ECD spectra with theoretically computed ones. Biological evaluations revealed that they did not show cytoprotective, antimicrobial, and α-glucosidase inhibitory activities.

Efficient synthesis of pyrazolopyridines containing a chromane backbone through domino reaction.

An efficient approach for the synthesis of pyrazolopyridines containing the aminochromane motif through a base-catalyzed cyclization reaction is reported. The synthesis was carried out through a three-component reaction of (arylhydrazono)methyl-4H-chromen-4-one, malononitrile, primary amines in the presence of Et3N at room temperature. However, carrying out the reaction under the same conditions without base led to a fused chromanyl-cyanopyridine. High selectivity, high atom economy, and good to high yields in addition to mild reaction conditions are the advantages of this approach.

Discovery of novel spiro[chromane-2,4'-piperidine] derivatives as potent and orally bioavailable G-protein-coupled receptor 119 agonists.

Herein, we describe the discovery, synthesis, and evaluation of a novel series of spiro[chromane-2,4'-piperidine] derivatives as G-protein-coupled receptor 119 agonists. Their initial design exploited the conformational restriction in the linker-to-tail moiety, which was a key concept in this study, to give lead compound 11 (EC50 = 369 nM, Emax = 82%). An extensive structure-activity relationship study resulted in the identification of the optimized drug candidate (R)-29 (EC50 = 54 nM, Emax = 181%). The defining structural features of the series were a terminal benzyl-type bulky substituent and a methylene linker between the sulfonyl and phenyl groups, both of which were in the head moiety as well as the spiro-type scaffold in the linker-to-tail moiety. An in vivo oral glucose-tolerance test using C57BL/6N mice showed that (R)-29 reduced glucose excursion at a dose of 3 mg/kg in a dose-dependent manner.

Synthesis of 2,2-Dialkyl Chromanes by Intramolecular Ullmann C-O Coupling Reactions toward the Total Synthesis of D-α-Tocopherol.

The complete synthesis of D-α-tocopherol was achieved using our developed-Ullmann C-O coupling reaction as a key reaction. The synthesis of the core structure of D-α-tocopherol, which is a chiral chromane, has never been reported using intramolecular Ullmann C-O coupling reactions owing to the low reactivity of electron-rich iodoarenes with tertiary alcohols. Because the developed intramolecular C-O coupling reactions prefer electron-rich iodoarenes with tertiary alcohols, we successfully synthesized the chiral chromane core and achieved the total synthesis of D-α-tocopherol.

New metathesis catalyst bearing chromanyl moieties at the N-heterocyclic carbene ligand.

The synthesis of a new type of Hoveyda-Grubbs 2(nd) generation catalyst bearing a modified N-heterocyclic carbene ligands is reported. The new catalyst contains an NHC ligand symmetrically substituted with chromanyl moieties. The complex was tested in model CM and RCM reactions. It showed very high activity in CM reactions with electron-deficient α,ß-unsaturated compounds even at 0 °C. It was also examined in more demanding systems such as conjugated dienes and polyenes. The catalyst is stable, storable and easy to purify.

The preventive and therapeutic consumption of meat enriched with carob fruit extract, rich in phenolic compounds, improves colonic antioxidant status in late-stage T2DM rats.

Oxidative stress is prevalent in Type 2 Diabetes Mellitus (T2DM) and has been associated with high meat consumption. Carob Fruit Extract (CFE) contains phenolic compounds, making it a suitable functional ingredient. Current study aims to evaluate the effect of CFE-enriched meat (CFE-meat) consumption on the antioxidant status of proximal and distal colon, and its relationship with fecal phenolic compounds in late-stage T2DM rats. Three groups of eight rats were studied: 1) D, fed control-meat; 2) ED, fed CFE-meat since the beginning of the study; 3) DE, fed CFE-meat after confirming T2DM. CFE-meat consumption reduces colonic oxidative stress mainly in the proximal section and helps to ameliorate glutathione metabolism and antioxidant score. Difference between ED and DE groups were associated with colon homeostasis and T2DM progression suggesting greater fermentation but lower absorption in the DE group. CFE appears as a promising tool to improve the antioxidant status observed in late-stage T2DM.

Design and synthesis of hydroxyethylamine (HEA) BACE-1 inhibitors: prime side chromane-containing inhibitors.

The structure activity relationship of the prime region of conformationally restricted hydroxyethylamine (HEA) BACE inhibitors is described. Variation of the P1' region provided selectivity over Cat-D with a series of 2,2-dioxo-isothiochromanes and optimization of the P2' substituent of chromane-HEA(s) with polar substituents provided improvements in the compound's in vitro permeability. Significant potency gains were observed with small aliphatic substituents such as methyl, n-propyl, and cyclopropyl when placed at the C-2 position of the chromane.

A novel monoterpene-stilbene adduct with a 4,4-dimethyl-2,3-diphenylchromane skeleton from Artocarpus xanthocarpus.

Artoxanthochromane (1), a DielsAlder-type conjugation product of 4-isopropenylresorcinol and oxyresveratrol, was isolated from the heartwood of Artocarpus xanthocarpus and characterized. The structure of 1 was elucidated as 2-(2,4-dihydroxyphenyl)-3-(3,5-dihydroxyphenyl)-7-hydroxy-4,4-dimethylchromane by 1D- and 2D-NMR spectroscopy, and other spectral evidences. A plausible metabolic mechanism was proposed to illustrate the biosynthetic pathway of artoxanthochromane. This compound exhibited mild mushroom tyrosinase inhibitory, and weak free radical-scavenging activities on ABTS(+.) and superoxide anion (O$\rm{{_{2}^{-{^\cdot} }}}$) free radicals.

Retrospective Review of Chromane Analogues as Anti-protozoal Leads: A Decade's Worth of Evolution.

Tropical, vector-borne, and neglected diseases with a limited number of medication therapies include Leishmaniasis, Malaria, Chagas and Human African Trypanosomiasis (HAT). Chromones are a large class of heterocyclic compounds with significant applications. This heterocycle has long aroused the interest of scientists and the general public from biosynthetic and synthetic points of view owing to its interesting pharmacological activities. Chromones and their hybrids and isomeric forms proved to be an exciting scaffold to investigate these diseases. The in vitro activities of Chromone, Chromane, and a panel of other related benzopyran class compounds against Trypanosoma brucei rhodesiense, Trypanosoma brucei gambiense, Trypanosoma cruzi, and numerous Leishmanial and Malarial species were investigated in our previous studies. The current article briefly describes the neglected diseases and the current treatment. This review aims to attempt to find better alternatives by scrutinizing natural and synthetic derivatives for which chromones and their analogues were discovered to be a new and highly effective scaffold for the treatment of neglected diseases, including compounds with dual activity or activity against multiple parasites. Additionally, the efficacy of other new scaffolds was also thoroughly examined. This article also discusses prospects for identifying more unique targets for the disease, focusing on flavonoids as drug molecules that are less cytotoxic and high antiprotozoal potential. It also emphasizes the changes that can be made while searching for potential therapies-comparing existing treatments against protozoal diseases and the advantages of the newer chromone analogues over them. Finally, the structure- activity relationship at each atom of the chromone has also been highlighted.

Effect of Sauropus androgynus L. Merr. on dengue virus-2: An in vitro and in silico study.

ETHNOPHARMACOLOGICAL RELEVANCE: Sauropus androgynus L. Merr. (Euphorbiaceae) commonly known as "multigreen" and "multivitamin" is consumed as a vegetable and used in traditional medicine to relieve fever. AIM OF THE STUDY: This in vitro study is aimed to explore the activities of the lipophilic fraction of the leaves of S. androgynus (LFSA) against dengue (DENV), chikungunya (CHIKV) viruses and malaria (P. falciparum strain 3D7) parasite. MATERIALS AND METHODS: The LFSA was analyzed by using GC-FID and GC-MS. The antiviral activity of LFSA was studied using the Vero CCL-81 cell line. The cytotoxicity assay was performed using 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). Focus forming unit (FFU), cell-based immunofluorescence (IFA) assays, and quantitative RT-PCR, were used to determine and confirm antiviral activity against DENV and CHIKV. The antiparasitic activity of LFSA was carried out against P. falciparum strain 3D7 grown in fresh O+ human erythrocytes culture. RESULTS: Twelve compounds were identified in LFSA using GC/MS. The most abundant compound was squalene (36.9%), followed by vitamin E (12.5%) and linolenic acid (10.2%). Significant reduction in DENV titre was observed under pre- and post-infection treatment conditions at a concentration of 31.25 µg/ml, but no anti-malarial and anti-CHIKV activity was observed. The Autodock-Vina-based in-silico docking study revealed that ß-sitosterol could form a strong interaction with the DENV E glycoprotein. CONCLUSION: Our findings suggest that LFSA can inhibit DENV infection and might act as a potent prophylactic/therapeutic agent against DENV-2. In-silico results suggested that ß-sitosterol may block the viral entry by inhibiting the fusion process.